What changes when accelerating over the bus. Overclocking the PC processor

What is overclocking? This is a change in the normal mode of operation of computer devices in order to increase their speed and improve the overall performance of the system. Apart from extreme overclocking, the goal of which is to squeeze the maximum out of a component and fix a record, overclocking makes it possible to meet the growing needs of applications and games without replacing equipment with more powerful ones.

Today I will show you how to overclock a processor (CPU). Let us consider the methods and means by which the performance and stability of an overclocked system are determined, as well as a simple way to return it to the “overclocked” state.

Before you start

Anyone can accelerate modern processors, even mobile, although the latter, according to their creators, is contraindicated due to the inability to provide adequate cooling. Yes, an overclocked "stone" (now and further we will mean stationary PC processors) consumes more energy and emits more heat, so the first thing to take care of is a good cooling system. It can be of both air and liquid type, the main thing is that the magnitude of its heat removal ( TDP) corresponded to or exceeded the thermal power of the "stone". For small and inconsistent overclocking, the boxed cooler that came with the CPU is sufficient, but under increased load it will most likely annoy you with loud noise.

The second important detail is the power supply unit (PSU). If his strength is barely enough for the current power consumption of devices, he will not pull overclock. To calculate the required power of the PSU, taking into account overclocking, use: select from the lists the components that are installed on your PC, and click " Calculate».

Calculator version « Expert”Allows you to take into account the voltage and cycles of the CPU after overclocking, as well as the percentage of load on it (CPU Utilization). Choose the latter to the maximum - 100%.

Happy experiments!

Precautionary measures

Attention! Overclocking a processor can damage the processor. If you do not have overclocking skills, then we strongly do not recommend overclocking yourself. Before you get started, check out your processor specification and visit the overclocking forums.

Below we have compiled tips to help you overclock safely:

1) If you are a beginner, only raise the processor frequency. It's better not to change the core voltage.

2) Increase the frequency in stages, by 100-150 MHz. This will avoid critical errors and processor overheating.

3) Perform system testing after each upgrade. This includes a stability test and continuous temperature monitoring. The temperature must be monitored throughout the entire overclocking process! If you exceed the allowed frequency, protection will be triggered and the settings will be reset. As the CPU frequency increases, its heat dissipation also increases. Prolonged exposure to extreme temperatures can damage the processor crystal.

4) If you also decide to increase the core supply voltage, then it should be done with the smallest possible step (usually 0.05V). However, the maximum limit should not exceed 0.3 volts, since increasing the voltage is more dangerous for your CPU than increasing the frequency.

5) Stop overclocking after the first unsuccessful stability test or when the permissible temperature is exceeded. For example, you have a 2.6 GHz processor. Its stable operation was observed at a frequency of 3.5 GHz. The first glitches appeared at 3.6 GHz. In this case, the overclocking stops and the last stable frequency is set, that is, 3.5 GHz.

Note: If your computer runs stably at the maximum frequency, but the CPU overheats, you should consider adding additional cooling or replacing the existing one.

Note 2 Notebooks are not very good candidates for overclocking, as their cooling options are quite limited. In this case, it would be more expedient to replace the components with more powerful ones.

Now we can go directly to overclocking.

Overclocking the processor

Step 1. Download the required utilities. You will need benchmarking and stress testing software to properly evaluate the overclocking results. It is also worth downloading programs that allow you to control the temperature of the processor crystal. Below we have provided a list of such programs:

CPU-Z is simple program monitor that will allow you to quickly see the current clock speed and voltage.

Prime95 is free program benchmarking which is widely used for stress testing. It is designed to run lengthy stress tests.

LinX is another stress testing program. A very convenient and flexible program for a processor stress test. This program loads the CPU by 100%. Therefore, sometimes it may seem that your computer is frozen. Most optimal for stability testing.

CoreTemp is a free program that allows you to monitor the temperature of the CPU die in real time. Can be used permanently in conjunction with the CoreTemp gadget. It also displays the current processor frequency, FSB bus and its multiplier in real time.

Before you start overclocking, run a basic stress test. This will give you a baseline to compare and also show if there are any stability issues.

Step 2. Check your motherboard and processor. Different boards and processors have different capabilities when it comes to overclocking. The first thing to watch is if your multiplier is unlocked. If the multiplier is locked, then overclocking will most likely fail.

Step 3. Open BIOS. It is through him that your system will be overclocked. To start it, press the "Del" key in the first seconds of starting the computer (when the POST screen appears).

Note: Depending on the model of your computer, the BIOS entry keys may vary. The main ones are "F10", "F2", "F12" and "Esc".

Step 4. Tabs may differ in newer and older BIOS versions. Usually older computers have BIOS versions AMI (American Megatrend Inc.) and Phoenix AWARD installed.

In the Phoenix AWARD, open the Frequency / Voltage Control tab. This menu may have other names such as "overclock".

In the AMI BIOS, this tab is called "Advanced" - "JumperFree Configuration" or "AT Overclock".

New computers are preinstalled with a UEFI BIOS version with full graphical interface... To find the overclocking menu, go to Advanced Mode and look for the AI Tweaker or Extreme Tweaker tab.

Step 5. Reduce the speed of the memory bus. This is to avoid memory errors. This option may be called "Memory Multiplier" or "Frequency DDR". Switch the option to the lowest possible mode.

Step 6. Increase the base frequency by 10%. This corresponds to approximately 100-150 MHz. It is also referred to as the bus speed (FSB) and is the base speed of your processor. As a rule, it is more low speed(100, 133, 200 MHz or more), which is multiplied by a multiplier, thereby reaching the full core frequency. For example, if the base frequency is 100 MHz and the multiplier is 16, the clock speed will be 1.6 GHz. Most processors can handle a 10% jump without issue. A 10% increase in frequency will correspond to a FSB frequency of 110 MHz and a clock speed of 1.76 GHz.

Step 7. Start the operating system and then stress test. For example, open LinX and run it for a few cycles. Open the temperature monitor in parallel. If there are no problems, you can move on. If the stability test fails or there is a sharp rise in temperature, then you must stop overclocking and reset the default settings. Do not let your processor reach 85 ° C (185 ° F).

Step 8. Continue steps 5 and 7 until the system becomes unstable. Run a stress test every time you raise your frequency. Instability is more likely to be caused by the processor not getting enough power.

Increasing the frequency through a multiplier

If your motherboard has an unlocked multiplier, overclocking can be done with it. Before you start increasing the multiplier, reset the base frequency. This will help you to fine tune the frequency.

Note: Using a lower base frequency and a large multiplier makes the system more stable, a higher base frequency with a lower multiplier gives a greater performance gain. Here you need to experimentally find the golden mean.

Step 1. Reset base frequency to default.

Step 2. Increase the multiplier. After you have lowered the base frequency, start raising it in the smallest increments (usually 0.5). The multiplier can be called "CPU Ratio", "CPU Multiplier" or something like that.

Step 3. Run stress test and temperature monitor exactly as in the previous section (step 7).

Step 4. Continue increasing the multiplier until the first glitches appear. Now you have the parameters on which your computer works stably. As long as your temperature readings are still within safe limits, you can start adjusting voltage levels to continue accelerating further.

Raising the core voltage

Step 1. Increase the processor core voltage. This item can be displayed as "CPU Voltage" or "VCore". An increase in voltage beyond the safe limits can damage not only the processor, but also the motherboard. Therefore, increase it in increments of 0.025 or the smallest possible for your motherboard... Excessive voltage jumps can damage components. And once again, we remind you: do not increase the voltage higher than 0.3 volts!

Step 2. Running a stress test after the first promotion. Since you left your system in an unstable state with a previous overclocking, it is quite possible that the instability will go away. If your system is stable, make sure the temperatures are still at an acceptable level. If the system is still unstable, try decreasing either the multiplier or the base clock speed.

Step 3. After you have managed to stabilize the system by increasing the voltage, you can return to raising either the base frequency or the multiplier (just as in the previous paragraphs). Your goal is to get maximum performance from minimum voltage. This will take a lot of trial and error.

Step 4. Repeat the cycle until the maximum voltage or maximum temperature is reached. Eventually, you will reach a point where you can no longer achieve performance gains. This is the limit of your motherboard and processor, and it is likely that you will not be able to get past this point.

In this material, a methodology for increasing the performance of the younger 4-core model of the LGA1151 platform - "Cor i5-6400" will be presented in stages. It is not possible to overclock this semiconductor crystal by changing the CPU frequency multiplier. But there is an alternative method, which will be described later.

Background

Up to a certain point, Intel Corporation provided the opportunity to increase the clock frequencies of its semiconductor solutions to computer enthusiasts, and this made it possible to achieve in practice a significant increase in performance. The last such generation of central processing units were solutions based on LGA1156. With the release of the next platform LGA1155, it was possible to increase the clock frequency only by changing the CPU frequency multiplier in processor models with the "K" index. All other semiconductor crystals of this family were deprived of this possibility. If they were used, it was possible to increase the bus frequency by 2-3 MHz only on some motherboard models and thereby obtain a slight increase in performance. A similar situation persisted over the next three generations of processors, and only with the release of LGA1151 certain changes were outlined in this direction. The architecture of the CPU has been redesigned, and after that the generator does not directly affect such PC components, as well.As a result, without changing the CPU multiplier, you can change the clock generator frequency (that is, and thereby increase the performance computer system... This is exactly how the i5-6400 is overclocked over the bus today.

Chip characteristics

First, let's take a look at the technical specifications of the Core i5-6400. The list of its parameters includes the following:

Release date - 3rd quarter of 2015.

The technical process is 14 nm.

The number of cores and program threads for processing code and data is 4.

The clock frequency range is 2.7-3.3 GHz.

3rd level cache - 6 MB.

The maximum amount of addressable RAM is 64 GB.

The number of active RAM channels is 2.

Integrated graphics accelerator- HD Graphics model 530 with an operating frequency range of 350-950 MHz.

Thermal package - 65 W.

The maximum temperature is 71 o C.

As you can see from the designation of this CPU model, there is no “K” index in its marking. Accordingly, it will not work to overclock it with the usual increase in the multiplier. Therefore, there is only one way to solve this problem - to increase the frequency and increase due to this speed of the "Cor i5-6400". Overclocking in this case is really justified: initially, the processor has significantly understated frequencies, and their increase will lead to a large performance gain against the background of other similar models with higher frequencies.

Overclocking features

Now let's note certain drawbacks that are associated with the increase in the level of performance of the processor solution Core i5-6400. Unlike the situation when the multiplier for the CPU with the index "K" simply increases, in this case, a number of possible problems do arise. These include the following:

The motherboard for overclocking the i5-6400 must be flashed with a special BIOS version. Formally, it was developed by the manufacturer of this computer component, but all possible problems that may arise after that, entirely fall on the shoulders of the owner of the PC, and the manufacturer in this case does not bear any responsibility.

After overclocking the semiconductor crystal, the integrated graphic solution... In most cases, such system units include discrete graphics card, and no problems arise. If in the process of work only the built-in solution is used, then overclocking is impossible.

Reduced performance of the AVX & AVX2 instruction. Fortunately, they are not very common in program code. But when it does, the performance is computing system will greatly decrease (it will be lower even than the normal mode of operation).

After this increase in performance, there is no way to control the temperature of the silicon chip in the CPU. Most sensors turn off or falsify readings. The only sensor that continues to function in this mode is the thermal converter of the CPU packaging, and this is quite enough in such a situation.

For overclocking, it is necessary to turn off all power-saving modes and the Turbo-boost technology. Their activation in the mode of increasing the speed leads to unstable work of the PC.

Essentially, there are no significant issues in the above list, and most overlockers don't even notice them.

system configuration

Now about the requirements for the PC configuration for such overclocking:

There must be a special version of the BIOS for the motherboard with an overclocking option.

Improved power supply with 700 watts or more.

RAM modules with a frequency of 3200 MHz.

Advanced cooling system for CPU and system unit.

Equipment preparation

Overclocking the i5-6400 processor on a motherboard with a regular BIOS is not possible. There is no default option to change the clock frequency. In order for it to appear, it is necessary to find a special firmware on thematic resources on the global web and download it. Then it needs to be installed in the base I / O system. After that, restart the PC and check for such an option. Only then can you try to overclock your PC.

Technique for increasing productivity

Now directly about the overclocking algorithm "Cor i5-6400". The overclocking of this silicon solution is as follows:

We download a special firmware for the BIOS of the motherboard, in which it is possible to change the frequency of the clock generator. Most overlocker forums have this information. Then we install it on our motherboard.

We reboot the computer system and go to the BIOS. Here we turn off the Turbo Boost option, all energy efficiency technologies, and the integrated graphics solution. We save the changes and restart the PC.

We check the stability of the system unit using the AIDA 64 utility.

Restart the computer again and go to BIOS. Here we reduce the frequency of work random access memory to a minimum (as much as the BIOS parameters of the motherboard allow), we increase the frequency of the clock generator with the smallest possible step. We save these parameters. We restart the system unit.

We retest the stability of the PC using the previously specified software... We continue to carry out the last two stages as long as the system is functioning stably. When just raising the frequency is not enough for stable operation, we use the voltage on the CPU. In practice, the frequency can reach 4.5-4.8 GHz, and the voltage - 1.4-1.425V, depending on the quality of the semiconductor crystal of the central processor, which underlies the PC. When these values are reached, further overclocking becomes impractical: the computer system then ceases to work stably.

Performance check after performance increase

After increasing the performance, it is necessary to check the stability of the functioning of the computing system based on Intel Core I5-6400. Overclocking, as noted earlier, negatively affects the execution of AVX & AVX2 instructions. Therefore, the test software should not include programs based on just such instructions. Most the best choice to check the stability of the computing system is in this case AIDA 64. This utility practically does not use the problematic program code. And there are versions of it in which such instructions are not used.

results

The increase in performance allows you to achieve phenomenal results from the "Cor i5-6400". Overclocking this chip allows you to get a performance level comparable to the flagship products of this manufacturer. At the same time, the difference in price is really impressive. The only exception in this regard is the software with instructions AVX & AVX2. But they are not that common, and this is unlikely to be a deterrent for most computer enthusiasts. Overclocking of such a solution is really justified. But it is important to understand: all this is done at your own peril and risk.

Best solution at the end of February 2017 to get the best gaming system performance. The picture may change as early as March with the release of AMD Ryzen, but we will check this after the publication restrictions are lifted and a detailed study of the platform with different video cards and a full set of games. Nevertheless, let's not forget: the desire to save money, especially if it is possible without prejudice to "opening the video card", is quite justified and possible. In 2016, such a "popular" model could be called the Intel Core i5-6400 SkyLake, which, moreover, the craftsmen quickly learned to overclock so that in many tests it was not inferior to the older Intel Core i5 6600K.

The "shop" was quickly shut down, blocking the possibility of overclocking with the release fresh versions BIOS, but as often happens, a number of models either received it belatedly or even did not receive a lock. Although even then there was always a rollback loophole BIOS version or firmware of "hacked" software. For a short time, the Intel Core i5-6400 will remain only in the secondary market, its glory is already continued by the Intel Core i5-7400 Kaby Lake, but for those who plan to repeat the overclocking trick, we recommend finding the previous generation. There is no major breakthrough, as in the case of the Core i7, the updates are more cosmetic. It is available in OEM and BOX versions. It makes sense to overpay if there is no cooling for the processor on hand, the buyer will find a good cooler with basic efficiency in the box.

Are there any differences? Of course, there are, first of all, they relate to reducing voltage and energy consumption. For comparison, the 3.3 GHz Intel Core i5 7400 takes a voltage of 1.056V, the Intel Core i5 6400 requires 1.12V. In compact cases, it will be possible to use it without using the fan or by reducing its speed as much as possible.

The internal structure has been preserved. 32 KB L1 cache, 256 KB L2 cache, 6 MB L3 cache. The maximum frequency is 3.5 MHz, the minimum is 800 MHz. Built-in Intel graphics HD Graphics 630.

Unfortunately, we did not see any prospects in terms of overclocking. The processor was installed on five motherboards: ASUS ROG MAXIMUS IX HERO, ASRock Z270 Extreme4, ASUS ROG Strix Z270F Gaming, ASUS PRIME Z270-K, ASUS TUF Z270 MARK 1. None of the boards allowed raising the frequency above 3.5 MHz. We can assume that overclocking via the bus with new processors has become impossible.

Intel Core i5-7400 Kaby Lake benchmarks

3DMark FireStrike

3DMark Cloudgate

Cinebench 15

WinRar (kB / s)

AIDA64 - Zlib

Power, W

Built-in graphics tests for example:
Dota 2, Medium

Minecraft, Fast

Tests with the video card KFA2 GeForce GTX 1060 OC:
GTA 5, Ultra, GTX1060

Results for Intel Core i5-7400 Kaby Lake

The most affordable quad-core processor Intel Core i5 7400 of the Intel Core i5 Kaby Lake family did not show an increase in performance, in general, in most tests it completely repeats the results of Intel Core i5 6400, and if we also take overclocking via the bus, it shows itself worse. The only benefit is reduced power consumption and improved compatibility when installed in a micro ITX chassis. Summing up, if streaming, video processing, and professional tasks are not planned, then it will become a good and successful basis for a home / gaming PC, coping with the load with dignity.

Comments:

2017-02-27 15:37:26 Guest:

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Those users whose acquaintance with the world personal computers began in the last century, the legendary Celeron 300A processors will probably remember. After all, overclocking as a mass phenomenon began with them. And there were good reasons for that: they easily overclocked at least one and a half times in frequency, and as a result, such a processor with a cost of about $ 150 reached the performance level of the older $ 700 Pentium II 450. This is what laid the ideological basis for overclocking: “Pay less - get more. "

However, the golden days of overclocking processors, fueled by the desire to save money, are long gone. Now overclocking has become a hobby for the rich, and those users who want to join the army of overclockers, on the contrary, are forced to pay more: all overclocking processors are subject to an additional markup. The last relatively inexpensive processor that could be overclocked to the level of senior representatives in the lineup was the Core i5-750 of the Lynnfield generation released in 2009. With a bit of luck, it was quite possible to heat it up to the performance provided by the Core i7 class processors. And by the way, the Clarkdale generation Core i3 processors produced at the same time were also quite overclocking.

But in 2011, the release of the LGA1155 platform and the next generation of Core processors put an end to all this wealth of opportunities available even in budget platforms. Conventional processors of the Sandy Bridge generation ceased to overclock completely, and overclockers were offered only two models to choose from: Core i5-2500K and Core i7-2600K, which Intel decided to sell a little more expensive than conventional and similar counterparts. As a result, the entrance ticket to the overclocking club began to cost $ 216 - this is exactly the amount that the overclocked Core i5 was priced at. However, this did not break the enthusiasts, and the sales of such expensive processors turned out to be quite decent. After all, there was clearly something to pay for. The operating frequency of the Core i5-2500K and Core i7-2600K could be raised to 4.8-5.0 GHz, while their nominal frequencies were 3.3-3.4 GHz. Therefore, after being a little outraged for the sake of decency, users still adopted the new overclocking paradigm, even though none of the CPU models below $ 200 could no longer be overclocked.

However, in recent times Intel's attitude towards overclocking began to change again. In the wake of the decline in interest in traditional PCs, it was the enthusiasts who turned out to be the most loyal buyers of the products of the microprocessor giant. Apparently, this melted the ice in the heart of Intel, and various signs of attention began to be shown to overclockers. One of the most obvious signs of this kind was the appearance of the Pentium G3258 Anniversary Edition - a budget 72-dollar processor designed specifically for overclocking. But although this processor has become a very popular toy in the hands of thrifty overclockers, it's hard to call it a full-fledged overclocker proposal. Pentium series offerings have only two cores and do not support Hyper-Threading technology, which cannot be compensated for by any increase in clock speed. Therefore, the Pentium G3258 is simply not suitable for serious systems.

With the release of the newest Skylake processors, many enthusiasts pinned their hopes for even greater concessions in terms of limiting the overclocking capabilities of Intel processors. The fact is that among the properties of the new LGA1151 platform was the ability to freely change the frequency of the base clock generator. And this promised the return of overclocking for any processors - starting with the youngest Pentiums, and ending with Core i5 and i7 processors without the letter K in the name. However, at first, the reality turned out to be somewhat different: in non-overclocking processors, Intel implemented a blocking of changing the clock frequency - this function received its own name BCLK Governor.

But after a few months after the announcement of Skylake, it became clear that such a blocking works exclusively at the software level and, accordingly, it is not difficult to get around it. Over the past weeks, motherboard manufacturers have been able to understand in detail the functioning of protection, and today we can definitely say that overclocking non-overclocking Skylake models is a reality. And by the way, judging by the absence of any opposition from Intel, such a victory over BCLK Governor does not really upset the processor manufacturer and occurs with its tacit consent (and maybe even with some assistance).

However, we will not delve into conspiracy theories, this material has a completely different purpose. The opened overclocking capabilities of any Skylake should certainly be checked. Therefore, we decided to test how it proceeds and what results the overclocking of the most interesting and correct objects from the point of view of the initial overclocking paradigm - the junior quad-core processor of the Core i5 series and the junior dual-core processor of the Core i3 series - can achieve.

Overclocking Locked Skylake: How It Works

So, in terms of overclocking the lineup Skylake processors do not differ at all in their structure from previous generations. Intel has introduced many sixth-generation dual-core and quad-core Core i3, i5 and i7 processors, but only two special models are allowed to overclock - the Core i5-6600K and the Core i7-6700K. These processors are slightly more expensive than similar models without the letter K in the name, but they have unlocked multipliers, and on motherboards with the Intel Z170 chipset, their resulting frequency easily changes to UEFI settings BIOS. For the rest of the Skylake family, this feature is not available, and this is a hardware limitation.

However, the clock speed at which the processor operates is actually the product of two parameters - the multiplier and the base frequency. And while in ordinary, not designed for overclocking processors, the multiplier is rigidly locked, for overclocking it still remains alternative way- by increasing the base frequency (BCLK) above the standard value of 100 MHz. The only problem is that in the latest Intel platforms for Sandy Bridge, Ivy Bridge and Haswell, the BCLK frequency was tightly connected not only with the processor frequency, but also with other frequencies in the system, for example, with the frequency of the DMI buses and PCI Express... And these tires, unfortunately, are very capricious and are extremely reluctant to operate at an increased frequency. An increase in their frequency by more than 3-5 percent will inevitably lead to distortion of the transmitted data. Therefore, changing the BCLK on motherboards for processors in LGA1150 and LGA1155 versions is completely useless - an increase in the base frequency above the nominal value causes instability or complete inoperability of the system as a whole.

But with the release of Skylake processors, Intel decided to make some changes to the usual frequency shaping scheme. In the new platform, the PCI Express bus and a set of system logic are separated into a separate domain, the frequency of which remains fixed regardless of how the BCLK changes.

Only the in-processor components remain tightly tied to the base BCLK frequency: computing cores, cache, integrated graphics core, memory controller and other Uncore-blocks that are synchronized exclusively with each other, and therefore treat overclocking with leniency. Thus, in theory, everything looks as if absolutely any Skylake processors are suitable for overclocking by changing the base frequency.

And overclocking Skylakes really do excellent overclocking not only by increasing the multiplier, but also by increasing the BCLK frequency. But despite this, the first attempts to change the Skylake frequency, not related to the K-series, did not bear any fruit. The fact is that in such processors Intel has built in protection against an increase in the base frequency - the BCLK Governor mechanism mentioned above, which did not allow the BCLK to be raised above 103-104 MHz. Fortunately, as we said earlier, this protection is not hardware in nature and can be bypassed at the software level. In order to learn how to overcome it, motherboard manufacturers had to spend several months. But the result has been achieved - for today, the algorithm for shutting down BCLK Governor by means Motherboard BIOS board found.

A breakthrough in this direction was made by Supermicro - it was on its C7H170-M board that the fundamental possibility of non-overclocker Skylake processors with a greatly increased BCLK frequency was demonstrated. And after Supermicro, other companies quickly implemented similar functionality. To date, almost all flagship motherboards from ASUS, ASRock, Biostar, Gigabyte, EVGA and MSI based on the Intel Z170 chipset have received special BIOS versions, which add the ability to fully control the BCLK frequency for the entire Skylake lineup. Moreover, according to the engineers, the same functionality, with some restrictions, can be transferred to motherboards with simpler logic sets, so overclocking by increasing the base frequency is likely to become available in very inexpensive platforms soon.

However, not everything is so simple. The implementation of bypassing Intel's protection requires some tweaks, as a result of which non-overclocked processors overclocked through an increase in BCLK acquire some flaws:

An overclocked processor completely loses control over the multiplication factor. This means that during bus overclocking, you will have to forget about Turbo Boost, Intel Enhanced SpeedStep technologies and energy-saving C-states. The CPU will always run at the limit frequency and with a constant supply voltage.
The ability to take temperature readings from temperature sensors built into the computing cores is no longer possible. Most monitoring tools simply cannot display the temperature of the processor cores.
The built-in graphics core turns out to be inoperative. This is expressed in the fact that Intel driver HD Graphics, when trying to run on an overclocked processor, immediately exits with an error.
The speed of execution of AVX / AVX2 instructions is significantly reduced.

In principle, the above list does not look too terrifying. Overclockers are not interested in energy-saving modes, especially since the processor does not consume too much in idle mode and without any decrease in frequency and supply voltage. It is not necessary to monitor the thermal mode of the CPU using core temperature sensors: for example, the built-in temperature sensor of the processor package (CPU Package) continues to regularly return correct readings during overclocking by increasing the BCLK frequency. Well, built-in graphics are generally considered by many to be nothing more than ballast in modern CPUs.

The only concern is the slowdown in AVX / AVX2 instructions. The performance of algorithms that actively use vector instructions can suffer many times over. But in fact, you can put up with this: gaming applications, in which the speed in which most overclockers are interested in the first place, practically do not use AVX commands.

Since now absolutely any Skylake generation processors can be overclocked by increasing the BCLK frequency, the overclocking of low-end models in each family is of the greatest practical interest. It is in this case that the principle “pay less - get more” can give the maximum effect. Taking into account the Skylake lineup that Intel has presented so far, we have compiled the following list of LGA1151 processors that are most suitable for overclocking:

CPU	Kernels / threads	L3 cache	Standard multiplier	Price	BCLK for 4.6-4.8 GHz
Core i7-6700
Core i5-6400
Core i3-6300
Core i3-6100
Pentium G4400

We did not check all the processors from this list, but chose only a couple of the most interesting ones: Core i5-6400 and Core i3-6100. It was with them that all practical experiments were carried out.

Overclocking BCLK: what in practice

In reality, everything works very simply. The only thing needed to overclock non-overclocking Skylake is the correct motherboard, for which there is an adapted BIOS version. Today, the list of suitable motherboards is already very large, but it should be borne in mind that not all manufacturers post BIOS versions with support for overclocking ordinary Skylake processors on their websites. Some of them, fearing the punishing hand of Intel, distribute the firmware necessary for overclocking in a guerrilla way - through independent overclocking forums. Therefore, before proceeding directly to overclocking, you will have to spend some time searching the version you want BIOS.

For example, the motherboard that is used for testing processors in our laboratory - ASUS Maximus VIII Ranger, has even received two BIOS versions suitable for overclocking Skylake with locked multipliers. But you need to look for them not on the ASUS website, but in a special topic on the overclocking portal HWBOT, although they are made by the company's programmers, not enthusiasts. It is worth noting that both of these versions are a fork from the main line of BIOS development and are intended solely for experiments on overclocking non-K processors. Moreover, the description file for these special firmware contains a warning that they are not suitable for overclocking a Core i5-6600K or Core i7-6700K and may even damage such processors.

The interface of special firmware does not differ at all from the usual UEFI BIOS environment: it does not add any additional options and only allows you to freely change the BCLK frequency. The only difference in the overclocking procedure is that for normal boot operating system in the UEFI BIOS settings under Advanced \ CPU Configuration will need to install the option BootPerformanceMode in value TurboPerformance and also disable CpuC-states and technology Intel SpeedStep... Otherwise, everything works exactly the same as when overclocking unlocked processors.

However, there is one more important preliminary remark to be made about checking the stability of the overclocked system. The fact is that common utilities that usually check stability, such as OCCT, LinX or Prime95, actively use resource-intensive AVX / AVX2 instructions, the execution of which is greatly slowed down in overclocked processors with a locked multiplier. Therefore, for non-overclocker processors, these utilities are unable to create a significant load, and to check temperature regime and the stability of work in general, they are no longer suitable. Use instead better programs, which can "puzzle" processor cores with intensive integer computations, among which we can recommend various packages for final rendering. However, even such programs do not warm Skylake too much, so in the end the maximum temperatures of overclocked non-K processors turn out to be noticeably lower than those of their full-fledged overclocking counterparts. Therefore, for non-overclocked processors, you can get by with even less powerful cooling systems than is usually used in platforms where overclocked Core i5-6600K or i7-6700K work.

Now about the results obtained. We did not set ourselves the goal of achieving any records. The task of the test is to reveal the overclocking potential of non-K-processors of the Skylake family, which can be revealed in mass systems. Therefore, to remove heat from the test CPUs, we used a conventional tower-type air cooler Noctua NH-U14S, and the processor voltage was not increased to potentially dangerous values. In other words, such overclocking, which will be discussed below, is operating modes that are quite acceptable for continuous operation.

The first we tried to overclock the quad-core Core i5-6400. This is a processor with an extremely low nominal 27x multiplier, so when overclocking it, the BCLK frequency needs to be raised quite a lot. However, there are no problems with this: when the supply voltage is increased to 1.425 V and the CPU Load-line Calibration option is enabled, our Core i5-6400 easily conquered the 4.7 GHz mark.

Stability in this state was confirmed by complete passing of the entire set of test applications, while the CPU temperature under load did not go beyond 80-degree limits. In other words, the overclocking was a success: the processor clock speed was increased by 75 percent higher than the nominal, and in terms of the achieved frequency, the Core i5-6400 turned out to be no worse than the thoroughbred overclocking Core i5-6600K. That is, at first glance, the Core i5-6400 allows you to save about $ 60 - this is the difference in the price of these quad-core processors.

But don't forget about the pitfalls. Temperature readings from the overclocked Core i5-6400 were not available. The utilities for monitoring the temperature of the processor cores really do not display any correct data.

As promised, the speed of the algorithms that use AVX / AVX2 instructions dropped dramatically. As an example, we ran three simple FPU tests from the Aida64 utility, and, as you can see from the above screenshots, the performance of the overclocked Core i5-6400 turned out to be several times worse than it should have been.

To better assess the scale of the disaster, in the following table we present the performance of these benchmarks for the Core i5-6400 in nominal mode and when it is overclocked to 4.7 GHz.

The frequency increases, but the performance decreases several times. This is the price to pay for overclocking the processor model that was not originally intended for overclocking. We can only console ourselves with the fact that programs that actively work with AVX / AVX2 instructions are not often found among applications familiar to most users.

The second processor we chose for tests, the Core i3-6100, is a junior dual-core processor with Hyper-Threading technology, originally designed to work at a frequency of 3.7 GHz. But by increasing the frequency of the BCLK, it turned out to be very easy to overclock it. The limiting frequency at which our sample was able to work normally was the same 4.7 GHz typical for Skylake. Operation in this mode required setting the BCLK frequency to 127 MHz, and stability was achieved by increasing the CPU supply voltage to 1.425 V.

No problems with the stable operation of the system were observed with this overclocking, the processor, on the other hand, warmed up to no more than 75 degrees. Thus, the frequency of the sample of Core i3-6100 we selected for tests was increased by 27 percent. This is noticeably less than the gain that was squeezed out of the Core i5-6400, but still not bad. Moreover, to this day, we have never been able to see a modern Core i3 in overclocking.

There are only two things to add to what has been said. First, in non-K processors, the frequency of the Uncore units is tightly linked to the frequency of the computational cores. Change in BIOS settings The multiplier responsible for the Uncore frequency does not affect non-overclocking processors in any way - this function works only for the Core i5-6600K and Core i7-6700K. Therefore, when overclocking non-K processors by increasing the BCLK frequency, the L3 cache is also overclocked simultaneously with the computational cores. Fortunately, there is no problem with that. As our experiments with Core i5-6400 and i3-6100 have shown, Skylake Uncore nodes function quite normally at higher frequencies together with computational cores and do not create any additional obstacles when overclocking to 4.7 GHz.

Secondly, no unpleasant surprises should be expected from the memory controller either. The Corsair Vengeance LPX CMK16GX4M2B3200C16R modules we used in the test system are designed for DDR4-3200 mode, and they were able to work normally in it, including at an increased BCLK frequency, with both tested CPUs. Naturally, an increase in the frequency of the base clock generator requires a concurrent increase in the dividers that form the memory frequency, and this should not be forgotten during overclocking. But overclocked non-K processors did not have any problems when working with high-speed DDR4 memory.

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